Locating earth faults in electrical systems



Se t.- 8, 1931. J, ONAS 1,822,701

LOCATING EARTH FAULTS IN ELECTRICAL SYSTEMS Filed Sept. 11', 1926 has/75% J Jonas,

Patented Sept. 8, 1931 J ULIUS JONAS, OF BADEN, SWITZERLAND, ASSIGNOE TO AKTIENGESELLSCHAFT BRONN BGVEEI 8., CIEL, OF BADEN, SWITZERLAND, A JOINT-STOCK COI'JIPANY OF SWITZERLAND LOCATING EARTH FAULTS IN ELECTRICAL SYSTEMS Application filed September 11, I926, SerialNo. 134,847, and in Germany October 14, 1925.

This invention pertains to method and ocating of earth faults in apparatus for tl" efectrical syrtei, particularly the selective location of faults as between different porot' a line.

A general object of the invention is the provision of method and means whereby the relative location of an earth fault in a high tension electrical system or network may be determined, as betw en d i'ercn't portions of the faulty line, in a simple and relirble manner.

Another object the provision of a method and means whereby the location of a fault as between ditFerent portions of the taulty line may be determined from the harmonic currents occuring as a result of the fault.

Other and further objects of the invention will be pointed out or indicated hereinafter or will appear o one skilled in the art upon an understan'fling ot the invention or its employment in practice.

In the drawing forming a part of this specification I illustrate in diagrammatic fashion one arrangement of apparatus whereby the invention may be practiced. but this is presented for purpose of illustration onlv and the invention claimed is not to be bonstrued as limited to employment of the specific apparatus shown.

In the drawing the figure is a diagram represent ng a line fed from two sources of electrieal'energy and eouipped with means for determining the locat n of a fault in the line as between ditlerent sections thereof.

When an earth faultoecurs in a high tensicn line, the current flowing to earth through the fault is largely capacia ive and is known as the fault current, or it the system is provided with inductive pr .oc'tive device; such blow out choking coils, may be termed the r-c.,- lual fault current. It the ear-thing reactance is tuned to resonance with the system, hen t current contains the watt and harmonic components of the rarth fault current. The harmonic component may be utinzed for the detect-ion of the faulty line by use of suitable instruments, such as a telephone receiver responsive to said component, which will indicate the faulty line by the loudness of tone resulting from the fact that such line carries the sum et all of the harmonics of the system, as pointed out in my (to-pending application Serial No. 80,082. The present invention has to do with the location of the fault as between dill rent sections of the line in which the fault exists, which sections are in series and may be receiving power from both ends. This is accomplished by the selective varia tion of impedance conditions in different sections of the line, whereby the harmonic cflects in the varioussections may be varied or ditr'erei-itiated, for purpose of comparison, and the location of the fault thus determined as between the various sections of the line. The nature of the invention will be understood with more particularity by reference to the illustrative arrangement shown in the drawing. Here A and B represent threephase power stations which are linked up electrically by the lines 10, 11 and 12 and protected by blow-out choking coils C atfording ear-thing reactance which is tuned to resonance with the system. At the stations A and B, or at other appropriate points, there are inserted in the lines 10, 11 and 12 transformers 15 and 16. 'Indicating instruments 17 and 18, which are perceptibly responsive to the harmonic effects occurring on the lines, may be connected to the secondaries of the transformers in the respective lines by means of the switching arrangements 19 and 20, so that a comparison of the conditions existi'n on the respective lines, as to the harmonics prevailing thereon, may be made by an auditory inspection. As between the lines thus inspected upon the occurrence of-a fault, the one productive of the most intense sound in the instrument will be the one in which the fault exists. For the purpose of determining the location of the fault as between different sections of the'faulty line, which in this instance may be considered line 12 which is grounded at the point F, provision is made for varying the impedance of the line, with respect to the indicative harmonic current, between the points where the inspecting instruments are linked to the line. To accomplish this there are linked with the line at any appropriate poini, or at various points, as at the junctions of the various sections of the line, choking coils 21, which are provided with short-circuiting connections 22, through which they may be sh rtcircuited by the switch device 2 T he choke coils, in their normal short-circuited condition, are Without detrimental effect upon the current harmonics, so that the current harmonics from F will in general be equally effective on the inspecting devices linked to the line at either side of them. opening the short-circuiting connect ons of the choke coil, however, it is rendered effective upon the line to raise the inductive resistance of the portion of the line on its side of the fault to the harmonic current, with the result that an appreciably greater part of the harmonic current will take the path toward the station on the opposite side of the fault. As a consequence, in the instance illustrated, the opening of the circuit of the choke coil on the side of the fault F toward the station B, will result in an increase of the flow of the harmonic current to station A, with the result that the intensity of sound in the instrument 1'? will be perceptibly in creased. Conversely, the intensity of sound in instrument 18 will be perceptibly decreased. It is thus definitely determined, from inspection of either instrument and comparison of its manifestations before and after the introduction of the effect of the choke coil, that the fault lies in the section of the line between-the choke coil and the station A. By the insertion of the choke coil at intervals, the fault may be definitely located, in this manner, in a particular section of the line. In this connection, only one set of such coils and the associated switch 24 have been shown for the purpose of illustrating howthe same may be embodied or connected in the system. It will be readily understood, however, hat any number of similar sets may be provided in like manner and distributed as desired, depend ing upon particular conditions.

The choking coils may be designed conveniently as twowinding transformers with secondaries which can be short-circuited or open-circuited as desired.

What I claim is:

1. In apparatus of the character described for the location of faults, a high tension network, protective earthing inductance associated with said network, polyphase lines forming part of said network, an indicating instrument responsive to harmonic currents, means for coupling the instrument with any one of said lines, and means providing for imposition of impedance on the selected line to which said instrument is coupled.

2. A method of locating a fault in an electrical transmission line, comprising first observing the abnormal harmonic current effects thereof existing therein as a result of a fault, followed by the imposition upon the line of an impedance to said harmonic currents and observing the effects of the abnormal harmonic currents then existing, and comparing the last mentioned said effects with the effects of said currents first observed.

3. A method of locating a fault in an electrical transmission line having protective earthing inductance, comprising observing the abnormal harmonic current effects existing on the line as a result of a fault, imposing an impedance at difierent points on the line, observing the harmonic current effects existing subsequent to such imposition of impedance and comparing said last mentioned effects with such effects first observed.

4. In a polyphase system comprising a plurality of electrical transmission conductors, the combination with a protective earthing inductance for the system, of impedance devices associated with said line conductors, means for selectively rendering the said devices effective to permit indicalion of the effects of abnormal harmonic currents in said line as a result of a fault therein, an indicating instrument responsive to such harmonic current effects, and means for selectively coupling said instrument to said conductors.

5. The combination with. a polyphase system comprising a plurality of electrical transmission conductors, and a protecting earthing inductance therefor, of impedance (ievices associated with said conductors for rendering effective means for indicating harmonic currents in said conductors resultfrom a fault therein, a device responsive to such harmonic currents, and means for selectively coupling said device to said conduciors to indicate the location of a fault in any of said conductors.

In testimony whereof I have hereunto subscribed my name this 25 day of August, A. D. 192-6, at Zurich, Switzerland.

JULIUS JONAS. 

